Drip Irrigation of Cotton with Treated Municipal Effluents: II. Nutrient Availability in Soil1
- A. Feigin,
- I. Vaisman and
- H. Bielorai2
The suitability of sewage effluent for drip irrigation of cotton (Gossypium hirsutum) growing on a deep calcareous clay soil (Typic Chromoxererts) was studied during three seasons. Secondary effluent was compared with freshwater at three application rates, the average of which for the three seasons were: low (350 mm yr−1), standard (440 mm yr−1), and high (515 mm yr−1). Fertilizer was applied with the fresh water in order to deliver amounts of nutrients (average for the 3 years) equivalent to those in the effluent that contained 150, 180, and 230 kg N; 32, 37, and 46 kg P; and 80, 100, and 120 kg K ha−1 yr−1 for the three rates, respectively. In addition, the standard amount of fresh water was given with half the quantity of fertilizer, and without fertilizer.
The concentration of available N and P in soil was increased greatly in all effluent and fertilizer-amended freshwater treatments, while available K in the soil was increased to a lesser extent. In general, at equivalent application levels, no significant differences in the level of available N, P, and K in the soil or in their uptake by plants, were detected between effluent and fertilizer-amended fresh water, although dry matter yield as well as N, P, and K accumulation were greater in the high-application-rate effluent treatment. The distribution of NO3-N in the soil profile was controlled by drip irrigation and practically no build-up of NO3− was detected below the 0- to 0.6-m depth layer during the irrigation period (in summer). However, during the rainy, winter season, heavy losses of residual NO3-N occurred, probably mainly through leaching.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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